yay fails with resource temporary unavailable when .cache is on zfs volume

[michaelhmich]

Affected Version

yay v12.3.5 - libalpm v14.0.0

Describe the bug

yay fails with lots of resource (files) temporary unavailable when .cache/yay is linked to zfs volume

setting BUILDDIR instead of linking gives the same problem

zfs property exec is on and no other restriction is active
compiling "manually" anything on the zfs volume works flawless

pacman.conf
CacheDir = /fotos/ARCH/pkg/
same zfs vol works without problem

unlinking and going back to .cache/yay on ext4 solves the issue, but not my space problem
I don't know how to debug this further and would need instructions for doing it
thanks